The present invention relates generally to a heat-developable image-recording material and a method of developing the same, and more particularly to a heat-developable image-recording material for photolithographic coatings, which gives high-contrast photographs and has excellent heat development properties and to a method for developing the same.
As one of the light exposure methods of photographic photosensitive materials, there has been known a method for image formation of so-called scanner type, wherein an original is scanned, and a silver halide photographic material is light-exposed based on the obtained image signals to form a negative or positive image corresponding to the image on the original.
As for a case where an image output from a scanner on a film is further printed directly on a printing plate without reversal step, or a scanner light source having a soft beam profile, a photosensitive material for scanners exhibiting ultra-high contrast property has been desired.
A large number of photosensitive materials comprising a support having thereon a photosensitive layer are known, where the image formation is performed by imagewise exposing the photosensitive material. Of these, a technique of forming an image by heat development is a system capable of satisfying the issue of environmental protection or simplifying the image formation means.
In recent years, reduction of the amount of waste processing solutions is keenly demanded in the field of photomechanical processes from the standpoint of environmental protection and space savings. To cope with this, techniques are required to produce heat-developable photosensitive materials for use in photomechanical processes, which can be effectively exposed by a laser scanner or laser image setter and can form a clear black image having high resolution and sharpness. Such heat-developable photosensitive materials can provide to users a heat development processing system being dispensable with use of solution-type processing chemicals, simple and freed from incurring environmental destruction.
Methods for forming an image by heat development are described, for example, in U.S. Pat. Nos. 3,152,904 and 3,457,075 and D. Morgan and B. Shely, Imaging Processes and Materials, xe2x80x9cThermally Processed Silver Systemsxe2x80x9d A, 8th ed., page 2, compiled by Sturge, V. Walworth and A. Shepp, Neblette (1969). The photosensitive material used contains a photo-insensitive silver source (e.g., organic silver salt) capable of reduction, a photocatalyst (e.g., silver halide) in a catalytic activity amount, and a reducing agent for silver, which are usually dispersed in an organic binder matrix. This photosensitive material is stable at room temperature. However, when it is heated at a high temperature (e.g., 80xc2x0 C. or higher) after the exposure, silver is produced through an oxidation-reduction reaction between the silver source (which functions as an oxidizing agent) capable of reduction and the reducing agent. The oxidation-reduction reaction is accelerated by the catalytic action of a latent image generated upon exposure. The silver produced by the reaction of the silver salt capable of reduction in the exposure region provides a black image and this presents a contrast to the non-exposure region. Thus, an image is formed.
Although heat-developable photosensitive materials of this type have hitherto been known, most of those photosensitive materials utilize a coating with a coating liquid containing as its solvent an organic solvent such as toluene, methylethylketone (MEK) and methanol in order to form a photosenstive layer thereon. Use of the organic solvent as the solvent is disadvantageous not only in terms of adverse effects on human bodies but also in view of costs for the recovery of the solvent or the like.
Thus, the following methods have been conceived in which a photosensitive layer (a term xe2x80x9caqueous photosensitive layerxe2x80x9d may also be usedhereafter) is formed using aqueous coating liquid which does not have the above-mentioned problems: For example, in JP-A-49-52626 and JP-A-53-116144, methods are described in which gelatin is used as a binder. In JP-A-50-151138, a method is described in which polyvinyl alcohol is used as a binder.
In JP-A-60-61747, a method using both gelatin and polyvinyl alcohol is described. In WO97/04355, a method is described in which a water-soluble or water-dispersed binder is used as the image-forming layer, and a water-soluble binder such as gelatin, polyvinyl alcohol, and cellulose derivative is used as a protecting layer. In JP-A-58-28737, an example of the photosensitive layer is described in which water-soluble polyvinyl acetal is used as a binder.
Indeed using these binders allows to form a photo-sensitive layer using water-soluble coating liquid, and is advantageous environmentally and economically.
If a polymer such as gelatin, polyvinyl alcohol, and water-soluble polyacetal is used as a binder, however, dehydration/shrinkage and thermal expansion of the binder occur simultaneously during heat development, wrinkles are generated in the film, and only films are obtained which are inappropriate for color print used by overlapping because the thermal expansion profile is different from that of the support.
On the other hand, an apparatus and a method for thermally developing a heat development recording material are generally well known (See e.g., U.S. Pat. No. 3,629,549 to Svendsen, U.S. Pat. No. 3,648,019 to Brewitz, U.S. Pat. No. 3,709,472 to Kreitz et al., and U.S. Pat. No. 4,518,845 to Svendsen).
Svendsen disclosed a developing apparatus having a thermally insulated drum attached concentrically in a heating material (See U.S. Pat. Nos. 3,629,549 and 4,518,845).
A film sheet to develop is connected with a drum to be driven with a fringe of a heating material. This type of heat development apparatus is, however, is not suited for a film having a comparatively soft thermoplastic polymer binder in its outermost layer. The surface of the side which supports emulsion contacts with an insulating drum or a heating material, so that the outermost layer of the film may receive scratch scars and/or adhesion marks.
Another type of heat development apparatus is equipped with a heating drum which electrostatically electrifies to hold the film during development. In this type of apparatus, the outermost layer of the film in the emulsion-supporting side does not contact either with the drum or other components, so that the above-mentioned scratch scars are not created. The electrostatic apparatus to hold a film on the drum during development is, however, comparatively complicated, and the shape is not suited to develop a large size of film.
Recently a thermal developing apparatus was disclosed in which small rollers are placed closely each other on a heating drum to hold a film between the drum and the small rollers to heat and transport (See WO97-13181).
This method is so well designed that a fold or scratch scar is not created on the film. When a heat development recording material is developed having a protection layer and/or a back layer in which latex of a polymer having a low glass transition temperature is used as a binder, however, such troubles may occur that irregular gloss is generated which is caused by adhesion of the surface of the drum or small rollers, or that irregular density is generated which is caused by thermal expansion of the film although this occurs seldom during development.
Therefore, technology has been required which provides a heat development photosensitive material 1) which is an environmentally and economically excellent aqueous photosensitive material, 2) which gives an coating surface having good quality, 3) which does not cause irregular density during development, 4) which is excellent in tolerance against scars, 5) which does not cause a xe2x80x9cjammingxe2x80x9d trouble in transport during heat development, and 6) which allows stable development for a long period, and a method for thermally developing the same.
The objective of the present invention is to provide a heat development photosensitive material 1) which has photographic properties such as high contrast and low overlapping for photolithography, particularly for scanner image setter, and 2) which has a stable heat development property for a long period, and a method for thermally developing the same.
The above objective was achieved by the following means:
1) A heat-developable image-recording material having a support, at least one image-forming layer on the support and at least one protecting layer on the image-forming layer,
said heat-developable image-recording material being developed by use of a heat development apparatus comprising a roller coming into a driving contact with a surface of said material on the side having said image-forming layer, said apparatus comprising a smooth surface coming into a sliding contact for transport with a surface of said material opposite to said surface on the side having said image-forming layer, wherein
at the temperature where said development is carried out, the ratio is 1.5 or more of the coefficient of friction between said surface on the side having said image-forming layer and a surface of said roller of said heat development apparatus, to the coefficient of friction between said surface opposite to said surface on the side having said image-forming layer and said smooth surface of said heat development apparatus.
2) A heat-developable image-recording material of 1), wherein said heat-developable image-recording material has at least one back layer on the opposite side to the side having said image-forming layer.
3) A heat-developable image-recording material of 2), wherein the outermost layer of said back layer contains a lubricant.
4) A heat-developable image-recording material of 1), wherein the outermost layer of said back layer contains a polymer binder having a glass transition temperature of 25xc2x0 C. or higher.
5) A heat-developable image-recording material of 1), wherein said protecting layer at the outermost surface contains a polymer latex as a binder.
6) A heat-developable image-recording material of 1), wherein said image-forming layer contains a polymer latex as a binder.
7) A heat-developable image-recording material of 1), wherein the side having said image-forming layer contains a compound represented by any one of formulae 1 to 3 or a hydrazine derivative: 
(In formula 1, R1, R2, and R3 are each independently H or a substituted group, and Z is an electron attracting group or silyl group. R1 and Z, R2 and R3, R1 and R2, or R3 and Z can bind each other to form a ring structure. In formula 2, R4 is a substituted group. In formula 3, X and Y are each independently H or a substituted group. A and B are each independently an alkoxy group, an alkylthio group, an alkylamino group, an aryloxy group, an arylthio group, or anilino group, X and Y, or A and B can bind each other to form ring structure.)
8) A heat-developable image-recording material of 7), wherein said hydrazine derivative is a compound having a chemical structure represented by formula H. 
(In the chemical structure, R12 is an aliphatic group, an aromatic group, or a heterocyclic group. R11 is H or a blocking group. G1 is CO, COCO, C(xe2x95x90S), SO2, SO, PO(R13) (R13 is selected in a way similar to R11; R13 and R11 can be different), or iminomethylene group. A1 and A2 are both H, or one of them is H and the other is a (substituted) alkylsulfonyl group, a (substituted) arylsulfonyl group, or a (substituted) acyl group, m1 is 0 or 1. When m1 is 0, R11 is an aliphatic group, an aromatic group, or a heterocyclic group.
9) A method of developing a heat-developable image-recording material having a support, at least one image-forming layer on the support and at least one protecting layer on the image-forming layer, by use of a heat development apparatus comprising a roller coming into a driving contact with a surface of said material on the side having said image-forming layer, said apparatus comprising a smooth surface coming into a sliding contact for transport with a surface of said material opposite to said surface on the side having said image-forming layer, wherein
at the temperature where said development is carried out, the ratio is 1.5 or more of the coefficient of friction between said surface on the side having said image-forming layer and a surface of said roller of said heat development apparatus, to the coefficient of friction between said surface opposite to said surface on the side having said image-forming layer and said smooth surface of said heat development apparatus.
10) A method of developing a heat-developable image-recording material of 9), wherein the surface of said roller of said heat development apparatus which makes contact with the surface on the side having said image-forming layer is made of silicone rubber.
11) A method of developing a heat-developable image-recording material of 9), wherein said smooth surface of said heat development apparatus which makes contact with said surface opposite to said surface on the side having said image-forming layer is formed of aromatic polyamide unwoven fabrics or Teflon (PTFE) unwoven fabrics.